Structure/function relationships of self-assembled triblock molecule nanostructures.

摘要

Supramolecular chemistry enables the self-assembly of molecules into well-defined objects on the nanoscale through non-covalent interactions. Molecular ordering within nanostructures affects the form and function of these materials at a scale inaccessible to conventional synthetic or lithographic techniques. Here, we explore the dendron rod-coil family of self-assembling molecules. Molecules in this family assemble in organic solvents into ribbon-like nanostructures with high aspect ratios. Synthetic modifications to the molecular structure of dendron rod-coils impact the supramolecular structure and function of these nanomaterials. We explore three sets of dendron rod-coil molecules with different modifications to the rod and coil portion of the molecule. Dendron rod-coil molecules synthesized with organic semiconducting blocks show enhanced conduction upon self-assembly due to increased ordering in their aggregated state. The ribbon-like nanostructures can be aligned in electric fields, and have implications in the bottom-up fabrication of organic electronic devices. Dendron rod-coil molecules synthesized with enantiomerically enriched coils self-assemble into chiral supramolecular nanostructures. The formation of chiral supramolecular structures is found to be highly solvent dependent, decoupling molecular and supramolecular chirality. The well-defined helical nanostructures are characterized in bulk and on the nanoscale by circular dichroism spectroscopy and atomic force microscopy, respectively. Experiments indicate that both R and S configurations of the molecules readily mix in a given nanostructure such that the helical sense is determined by the stereochemistry of the majority component. The association of inorganic precursors with the chiral nanostructures enables the templated mineralization of inorganic mineral. The fabrication of chiral supramolecular objects on the appropriate scale has implications in catalysis, biorecognition and electronics. Finally, dendron rod-coil molecules were synthesized incorporating polymerizable groups for the post-modification of assembled dendron rod-coil nanostructures. The polymerizable groups have the potential to impart solvent and thermal stability in addition to electronic function to the self-assembled nanostructure. The exploration of the three sets of dendron rod-coil molecules has furthered our understanding of self-assembly in dendron rod-coil compounds, showing their remarkable tolerance to changes in molecular structure. By tuning the molecular structure and solvent environment, we have been able to show precise control over the form and function of these supramolecular structures on the nanometer scale.